Warfarin prevents and treats blood clots. Don't drink alcohol while on warfarin. Don't make changes in your diet (eating large amounts of green, leafy vegetables) as this may affect how it works.
Warfarin is a prescription medication used to lower the chances of blood clots forming in your body due to various causes. Warfarin belongs to a group of drugs called anticoagulants or "blood thinners". It helps prevent blood clots from forming by decreasing the formation of substances in the blood known as clotting factors. Careful monitoring of side effects is required using regular blood tests.
This medication comes in tablet form. It is also available in an injectable form to be infused into a vein by a healthcare provider at a hospital or other medical facility. Warfarin is usually taken once daily, with or without food. The dosage will vary depending on the results of your PT/INR test (blood test).
Common side effects of warfarin are nausea, vomiting, and an altered sense of taste. Seek medical attention if you experience bruising or bleeding.
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Warfarin Cautionary Labels
Uses of Warfarin
Warfarin is a prescription medication used to lower the chances of blood clots forming in your body due to various causes.
This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.
Warfarin Brand Names
Warfarin Drug Class
Warfarin is part of the drug class:
Side Effects of Warfarin
Warfarin can cause serious side effects. See "Drug Precautions" section.
Common, less serious side effects include:
- changes in taste
- stomach pain
- hair loss
This is not a complete list of warfarin side effects. Ask your doctor or pharmacist for more information.
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088
Many medicines, including prescription and non-prescription medicines, vitamins and herbal supplements can interact with warfarin and affect the dose you need, or increase warfarin side effects.
Some of the medications known to interact with warfarin are:
- ibuprofen (Motrin, Advil)
- naproxen (Aleve)
- acetaminophen (Tylenol)
- some antibiotics
- cold medicines
- allergy medicines
- birth control pills
There are many more medicines that interact with warfarin. Before taking a new medicine, check with your doctor or pharmacist to be certain it won't interact with warfarin.
- Do not take other medicines that contain warfarin.
Warfarin can cause serious side effects. Call your healthcare provider right away if you get any of the following signs or symptoms of bleeding problems:
- pain, swelling, or discomfort
- headaches, dizziness, or weakness
- unusual bruising (bruises that develop without known cause or grow in size)
- bleeding gums
- bleeding from cuts takes a long time to stop
- menstrual bleeding or vaginal bleeding that is heavier than normal
- pink or brown urine
- red or black stools
- coughing up blood
- vomiting blood or material that looks like coffee grounds
Serious side effects of warfarin also include:
- death of skin tissue (skin necrosis or gangrene). This can happen soon after starting warfarin. It happens because blood clots form and block blood flow to an area of your body. Call your healthcare provider right away if you have pain, color, or temperature change to any area of your body. You may need medical care right away to prevent death or loss (amputation) of your affected body part.
- “purple toes syndrome.” Call your healthcare provider right away if you have pain in your toes and they look purple in color or dark in color.
Other side effects with warfarin include:
- allergic reactions
- liver problems
- low blood pressure
- low red blood cells
Do not take warfarin if:
- your chance of having bleeding problems is higher than the possible benefit of treatment. Your healthcare provider will decide if warfarin is right for you. Talk to your healthcare provider about all of your health conditions.
- you are pregnant or plan to become pregnant. Warfarin can cause death or birth defects to an unborn baby. Use effective birth control if you can get pregnant.
- you are allergic to warfarin or to anything else in warfarin.
What to Avoid:
- Do not start, stop, or change any medicine without talking with your healthcare provider.
- Do not make changes in your diet, such as eating large amounts of green, leafy vegetables.
- Do not change your weight by dieting, without first checking with your healthcare provider.
- Avoid drinking alcohol.
- Do not do any activity or sport that may cause a serious injury.
Warfarin Food Interactions
Some foods can interact with warfarin and affect your treatment and dose.
Eat a normal, balanced diet. Talk to your doctor before you make any diet changes. Do not eat large amounts of leafy green vegetables. Leafy green vegetables contain vitamin K. Certain vegetable oils also contain large amounts of vitamin K. Too much vitamin K can lower the effect of warfarin.
Avoid drinking cranberry juice or eating cranberry products.
Avoid drinking alcohol.
Tell your healthcare provider about all of your health conditions, including if you:
- have bleeding problems
- fall often
- have liver or kidney problems
- have high blood pressure
- have a heart problem called congestive heart failure
- have diabetes
- drink alcohol or have problems with alcohol abuse. Alcohol can affect your warfarin dose and should be avoided.
- are pregnant or breastfeeding
Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements.
Warfarin and Pregnancy
Tell your doctor if you are pregnant or planning to become pregnant. Warfarin should not be taken during pregnancy. Warfarin can cause death or birth defects to an unborn baby.
The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.
Warfarin falls into 2 categories: D for women with mechanical heart valves, and X for all other pregnant women. It has been shown that use of warfarin in pregnant women caused some babies to be born with problems. However, because women with mechanical heart valves are at a high risk of thromboembolism (blood clot in blood vessel), the benefits of taking warfarin may outweigh the risks.
Talk to your doctor about the risks of taking warfarin during pregnancy.
Warfarin and Lactation
Studies have shown that warfarin is not excreted in human milk. Caution should be exercised if you are breastfeeding and also taking warfarin.
- Get your regular blood test to check for your response to warfarin. This blood test is called a PT/INR test. The PT/INR test checks to see how fast your blood clots. Your healthcare provider will decide what PT/INR numbers are best for you. Your dose of warfarin will be adjusted to keep your PT/INR in a target range for you.
- Call your healthcare provider if you are sick with diarrhea, an infection, or have a fever.
- Tell your healthcare provider about any planned surgeries, medical or dental procedures. Your warfarin may have to be stopped for a short time or you may need your dose adjusted.
- Call your healthcare provider right away if you fall or injure yourself, especially if you hit your head. Your healthcare provider may need to check you.
- Always tell all of your healthcare providers that you take warfarin.
- Wear or carry information that you take warfarin.
- Take warfarin exactly as prescribed. Your healthcare provider will adjust your dose from time to time depending on your response to warfarin.
- Take warfarin at the same time every day. You can take warfarin either with food or on an empty stomach.
- If you miss a dose of warfarin, call your healthcare provider. Take the dose as soon as possible on the same day. Do not take a double dose of warfarin the next day to make up for a missed dose.
- Call your healthcare provider right away if you take too much warfarin.
- This medication is available in an injectable form to be given directly into a vein (IV) by a healthcare professional.
Take warfarin exactly as your doctor prescribes it. Follow the directions on your prescription label carefully.
Your doctor will adjust your dose from time to time depending on your response to warfarin based upon your PT/INR.
If you take too much warfarin, call your healthcare provider or local Poison Control Center, or seek emergency medical attention right away.
If warfarin is administered by a healthcare provider in a medical setting, it is unlikely that an overdose will occur. However, if overdose is suspected, seek emergency medical attention.
Store at controlled room temperature and protect from light. Keep this and all medicines out of the reach of children.
Warfarin FDA Warning
- Warfarin sodium can cause major or fatal bleeding. Bleeding is more likely to occur during the starting period and with a higher dose (resulting in a higher INR).
- Risk factors for bleeding include high intensity of anticoagulation (INR greater than 4), age 65 or older, highly variable INRs, history of gastrointestinal bleeding, hypertension, cereberovascular disease, serious heart disease, anemia, malignancy, trauma, renal insufficiency, concomitant drugs, and long duration of warfarin therapy.
- Regular monitoring of INR should be performed on all treated patients. Those at high risk of bleeding may benefit from more frequent INR monitoring, careful dose adjustment to desired INR, and a shorter duration of therapy.
- Patients should be instructed about prevention measures to minimize the risk of bleeding and to report immediately to physicians the signs and symptoms of bleeding.